<html>
<head>
  <meta charset="UTF-8">
</head>
<body>
<div id="app" onmousemove="toggle(event)" onmouseleave="mouseleave()">
  鼠标挪到这里
</div>
<div id="msg">展示的内容</div>
</body>
</html>
<script>
  var msg=document.getElementById('msg');
  function toggle(e) {
      msg.style.position='fixed';
      msg.style.display='block';
      msg.style.left=e.pageX+'px';
      msg.style.top=e.pageY+'px';
  }
  function mouseleave() {
    msg.style.display='none';
  }
  console.log('ssada'.includes(''));
</script>
<style>
#app {
  width: 100px;
  height: 100px;
  background:red;
  color: white;
}
  #msg {
    display: none;
    width: 100px;
    height: 20px;
    background: #aaaaaa;
  }

</style>
